Not much, if this Atlantic article is to be believed. Basically the researchers found that women with 2 or more kids were actually more productive, in terms of publications, than women with 1 kid or none. (The exception was right after having a baby, and also with preteens–all that angst, I guess.) This makes a certain amount of sense to me–economists seem like planners, on the whole, and women who are successful in that field most likely try to time their families to when is convenient–but it’s still nice to hear some validation that having kids doesn’t automatically make you a less than stellar worker.